The demand for Quality of Service (QoS) and resource admission control (RAC) in access and aggregation networks is increasing with the emerging interest of network operators in triple play services, i.e. concurrent deployment of High Speed Internet (HSI) access, conversational point-to-point services such as VoIP or conversational IP multimedia services, and client-server based services such broadcast TV (BTV).
Multicast or broadcast applications like broadcast TV typically rely on a terminal or customer premises equipment (CPE) triggered mechanism to reserve resources in the access network. The end-user's set-top box (STB), PC or home gateway for instance uses the Internet Group Multicast Protocol (IGMP) to select a TV channel or to zap between TV channels, thereby requesting reservation of the necessary resources in the access network to deliver the TV channel. Note that different TV channels indeed may have different resource or Quality of Service (QoS) requirements in the access and aggregation network depending for instance on the definition (standard definition versus high-quality definition) or the availability of the channel in the access node versus a situation where the channel has to be retrieved from nodes deeper in the network. The access node, for instance the Digital Subscriber Line Access Multiplexer (DSLAM) in case of a DSL access network, terminates the IGMP messages received from the CPE and performs resource admission control on the basis of its knowledge of available resources on the DSL line towards the customer premises and the locally configured bandwidth profile for broadcast TV in the first mile. The admission control for services like broadcast TV must be done as closely as possible to the CPE, i.e. preferably in the access node, because the delay for zapping between channels must be as small as possible in order to achieve an acceptable user experience.
Conversational services such as VoIP, video conferencing and fixed IMS on the other hand typically use a network triggered resource reservation mechanism whereby application-proxies make the resource reservations in the network. Examples are a gaming server or an IP Multimedia Subsystem (IMS) that issues resource reservation requests from its Proxy-Call State Control Function (P-CSCF) to a central resource admission control subsystem somewhere in the aggregation network. Thereto, the IMS P-CSCF is equipped with a so called Gq interface, Gq′ interface or ETSI Tispan interface as specified in the draft ETSI Specification ES 282 300 version 1.6.6, published in October 2005 under the title “NGN Functional Architecture; Resource and Admission Control Subsystem (RACS); Release 1”. The central resource admission control subsystem typically is integrated in a separate device like a Session Resource Broker or SRB, but could also be integrated in the IMS. The application servers/proxies for unicast services like VoIP and VoD send resource reservation requests to this central resource admission control function. The latter is supposed to have a logical overview of the available resources in the aggregation network (and eventually on the access links). Based on its knowledge of these available resources, the central admission control function grants or refuses the requests from the application servers/proxies.
A problem with the existing solution based on central resource admission control for network triggered reservation requests is that the central RAC function does not know how the amount of bandwidth (or resources) that is dynamically reserved by the access nodes for CPE originating reservation requests. In case of broadcast TV deployment for instance, the central RAC function is only aware of the first time a subscriber switches on his set-top box to receive BTV (assuming that the video platform indicate to the central RAC function that BTV is active). Afterwards, the central RAC function is not informed on channel zapping by the customer although such channel changes may impact the availability of resources in the access and aggregation network. BTV channels may have different resource requirements (e.g. standard-definition versus high-definition BTV). Moreover, not all BTV channels may be available at the access node and consequently may need to be retrieved from nodes deeper in the aggregation network. The uplink interface of the access node may be congested and/or the downlinks from the access node to the customer premises may be congested. Since the central RAC function is unaware of the channel zapping, these congestion problems may remain invisible to the central RAC function that consequently may grant network triggered resource reservation requests for which insufficient resources are available.
Similarly, the access node that terminates the customer premises originating resource reservation requests for multicast applications is not aware of the amount of bandwidth that is allocated by the central RAC function for unicast applications. A consequence of this is that requests for multicast services could be accepted by the access node while there is insufficient bandwidth in the aggregation network to deliver the requested channel or service.
Currently no adequate solution exists that coordinates resource admission control for both network triggered resource reservation requests and terminal triggered resource reservation requests.
A straightforward way to coordinate admission control for both terminal and network triggered resource reservation requests would be network planning. Network planning implies that available bandwidth (or resources) on various network links is (are) partitioned into a bandwidth (or resource) budget for conversational services (IMS, VoIP, VoD) and a bandwidth (or resource) budget for multicast applications (BTV). This approach however is highly inefficient because bandwidth budgets that are dedicated to a certain type of service (e.g. BTV) cannot be used by other services. As a result of network planning, the capacity in the access and the aggregation network is rigidly segmented between the services that require QoS, such as BTV, VoD, VoIP and IMS services. For the DSL access links for instance a bandwidth budget will be reserved for VoIP (typically dimensioned to enable a few simultaneous VoIP or Video Telephony calls) and a separate bandwidth budget will be reserved for video services such as BTV and VoD (if assumed that the video budget may be shared between BTV and VoD). As a consequence, voice and video traffic must not exceed their respective planned bandwidth budgets. This means that a dedicated portion of the capacity of the first mile is dedicated to BTV/VoD, which cannot be used for other services like VoIP or IMS. For a set-top box that can access BTV/VoD and IMS, the maximum bandwidth on the first mile of for instance 6 Mbps may be divided into 5 Mbps that will be available to BTV/VoD, while the remainder portion (1 Mbps) will be available to services like IMS. Obviously, other segmentations may exist as well. This division of the resources will be frozen. Network planning that segments the resources between video services and other services in such a way obviously results in inefficient resource usage. In particular when resource hungry conversational services will emerge (IMS, point-to-point video services, etc.), the network planning approach will no longer be adequate. Indeed, since IMS will be the future main system for conversational multimedia services and since IMS is not limited to VoIP only, the resource requirements for services that use network triggered reservation request mechanisms will increase dramatically.
As a conclusion, it is an objective of the present invention to provide a solution to the above explained drawbacks of handling CPE triggered resource reservation requests in access nodes, handling network triggered resource reservation requests in a central RAC device, and eventually using network planning to divide that resource budget in the access and aggregation network between the different types of services.